Справочник Пользователя для Pelco MD2001-X
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Pelco Manual C616M-B (11/97)
4.4 NORMAL OPERATION
During normal operation, the motion detector may be set with all toggle switches in
the active mode (up position). This displays the detection window, arms the four
action indicators (LED, Logic output, relay contact, and buzzer) and activates the
AUTO reset. It allows the operator to look away from the monitor and quickly locate
the detection window on the screen. If the operator wishes to turn the alert indica-
tors off and reset sooner, the manual reset button can be used.
the active mode (up position). This displays the detection window, arms the four
action indicators (LED, Logic output, relay contact, and buzzer) and activates the
AUTO reset. It allows the operator to look away from the monitor and quickly locate
the detection window on the screen. If the operator wishes to turn the alert indica-
tors off and reset sooner, the manual reset button can be used.
If the motion detector is used to view a critical area during a non-critical time period, such
as a door at quitting time, the ARM switch may be set to OFF (down position). In this
mode the ALRT LED will flash, but the audio signal and auxiliary output will not activate.
as a door at quitting time, the ARM switch may be set to OFF (down position). In this
mode the ALRT LED will flash, but the audio signal and auxiliary output will not activate.
4.5 SYSTEM CONSIDERATIONS
Motion detectors operate on the principle that any change in the camera field-of-view
is caused by some moving object. They monitor the content of the camera field-of-view
within a sensitized area and detect differences in the scene content in that area
from one TV frame to the next. Moving objects in the detection area field-of-view
cause video changes which, depending on the sensitivity setting, cause alerts. How-
ever, particularly in outdoor installations, normal motions such as blowing leaves,
small animals, birds, or clouds may cause unwanted alerts. Other factors, such as
instability in the camera, rapid changes in light level caused by an auto-iris, jitter
caused by camera interlace, or electrical noise signals superimposed on the video
signal by improper cabling or poor grounding will also cause changes in the scene
content and produce false alerts. The sensitivity adjustment establishes the amount
of change in scene content that is required within the detection area before the unit
produces an alert. Reducing the sensitivity will reduce unwanted or false alerts. How-
ever, sensitivity to desired alert conditions is also reduced. Other important system
considerations for achieving optimum motion detector performance are discussed in
the following sections.
is caused by some moving object. They monitor the content of the camera field-of-view
within a sensitized area and detect differences in the scene content in that area
from one TV frame to the next. Moving objects in the detection area field-of-view
cause video changes which, depending on the sensitivity setting, cause alerts. How-
ever, particularly in outdoor installations, normal motions such as blowing leaves,
small animals, birds, or clouds may cause unwanted alerts. Other factors, such as
instability in the camera, rapid changes in light level caused by an auto-iris, jitter
caused by camera interlace, or electrical noise signals superimposed on the video
signal by improper cabling or poor grounding will also cause changes in the scene
content and produce false alerts. The sensitivity adjustment establishes the amount
of change in scene content that is required within the detection area before the unit
produces an alert. Reducing the sensitivity will reduce unwanted or false alerts. How-
ever, sensitivity to desired alert conditions is also reduced. Other important system
considerations for achieving optimum motion detector performance are discussed in
the following sections.
4.6 CAMERA SELECTION
The MD2001 may be used with both 2:1 interlace and random interlace cameras.
No external sync drive from the camera is required. These features are exceptional
in motion detection systems.
No external sync drive from the camera is required. These features are exceptional
in motion detection systems.
Nevertheless, camera selection is very important. The selected cameras should be
electrically and mechanically stable, low-noise, high quality units for best performance.
electrically and mechanically stable, low-noise, high quality units for best performance.
In general, random interlace cameras will give a lower level of performance than
2:1 interlace cameras. Small disturbances of the image are inherent with random
scanning. These disturbances may be interpreted by the motion detector as object
motions. Consequently, a system using random interlace cameras will require a
slightly lower sensitivity setting to minimize false alerts.
2:1 interlace cameras. Small disturbances of the image are inherent with random
scanning. These disturbances may be interpreted by the motion detector as object
motions. Consequently, a system using random interlace cameras will require a
slightly lower sensitivity setting to minimize false alerts.
4.7 LENS SELECTION
Video motion detector systems are primarily affected by three lens parameters:
Focal length, Lens Aperture and the Iris control method.
Focal length, Lens Aperture and the Iris control method.
4.7.1 Focal Length
The focal length of a lens directly affects the apparent size of objects as seen on
the monitor and by the motion detector. Focal length also affects the overall camera
field-of-view. A long focal length (telephoto) lens magnifies objects in the scene, but
covers a smaller area. A short focal length (wide-angle) lens covers a large overall
scene, but shrinks the apparent size of objects in the scene. Motion detectors can
be affected by lenses that are too short or too long in focal length.
the monitor and by the motion detector. Focal length also affects the overall camera
field-of-view. A long focal length (telephoto) lens magnifies objects in the scene, but
covers a smaller area. A short focal length (wide-angle) lens covers a large overall
scene, but shrinks the apparent size of objects in the scene. Motion detectors can
be affected by lenses that are too short or too long in focal length.
A long focal length (telephoto) lens is often used outdoors to view distant areas.
These lenses magnify the effects of camera motion. It is important for the camera
to have a stable mount. Avoid unsteady towers or poles. Telephoto lenses also
magnify the disturbances caused by atmospheric effects, such as the image “swim-
ming” seen when hot air currents cause air density changes in the path between
the camera and what is being viewed.
These lenses magnify the effects of camera motion. It is important for the camera
to have a stable mount. Avoid unsteady towers or poles. Telephoto lenses also
magnify the disturbances caused by atmospheric effects, such as the image “swim-
ming” seen when hot air currents cause air density changes in the path between
the camera and what is being viewed.